The invention relates to a rotary piston machine, comprising a housing which has a cylindrical housing inner wall, and at least one piston which is arranged in the housing and which can rotate about a longitudinal mid-axis of the housing and at the same time executes, by means of a control mechanism, a to-and-fro linear movement which serves for periodically enlarging and reducing at least one chamber assigned to the piston.
A rotary piston machine of this kind is known from DE 100 01 962 A1.
Such a rotary piston machine is used preferably as an internal combustion engine.
Rotary piston machines belong, in general, to a type of machine in which one or more pistons rotate in a housing, a further type of movement normally being superimposed on the rotational movement of the piston or pistons, in order periodically to enlarge and reduce in volume the one or more chambers which are assigned to the piston or pistons and which conventionally form the working chambers for a Carnot cycle.
In the rotary piston machine known from DE 100 01 962 A1, a plurality of pistons are arranged so as to be distributed circumferentially about the housing mid-axis of the housing. The pistons are mounted radially moveably in the housing, the control mechanism deriving the radially directed to-and-fro stroke movement of the pistons from the rotational movement of the pistons.
When the known rotary piston machine is used as an internal combustion engine, the individual working strokes of admission, compression, expansion and expulsion are therefore implemented by means of the radially directed to-and-fro stroke movement of the individual pistons.
The control mechanism of the known rotary piston machine has a fixed cam piece arranged approximately in the centre of the housing, the pistons each having at least one running member on their side facing the housing mid-axis, the pistons being guided along the control cam by means of the said running members. Furthermore, the control mechanism is designed in such a way that in each case adjacent pistons of the radially moveable pistons execute an oppositely directed stroke movement. The pistons of the known rotary piston machine have in each case a toothing on their end faces leading and trailing in the direction of rotation of the pistons, and between the end faces of adjacent pistons in each case is arranged a co-rotating shaft which is provided with a toothing and which is in meshing engagement with the toothings of the two adjacent end faces of the pistons.
One disadvantage of this known rotary piston machine may be seen in that the radially directed linear movement of the pistons takes place alternately in the direction of and counter to the action of the centrifugal force and the action of the centrifugal force. In this case, because of the radially directed stroke movement of the individual pistons, the mass distribution with respect to the longitudinal mid-axis of the housing and consequently also the moment of inertia of the pistons change constantly. Moreover, because of the centrifugal forces and the mechanical coupling in each case of adjacent pistons moving radially in opposition, the cam piece which is located in the centre of the housing and is fixed relative to the housing and which serves for guiding the pistons is subjected to load exerted by forces.
Another type of rotary piston machine is known from WO 98/13583, in which the individual pistons rotating in the housing are designed as pivoting pistons which, during their rotational movement, additionally execute rocker-like to-and-fro pivoting movements in the housing. The control mechanism for controlling the rocker-like to-and-fro pivoting movements of the individual pistons corresponds virtually identically to the control mechanism of the abovementioned known rotary piston machine with pistons radially moveable linearly.
In this pivoting piston machine, too, a disadvantage may be seen in the mass distribution which is not optimum with respect to the longitudinal mid-axis of the housing or in the incomplete cancellation of the resultant centrifugal forces of the individual pistons.
The invention is based on the object to provide a new kind of a rotary piston machine in which the periodic alteration of the volume of the at least one chamber is achieved in another fashion.